Weight reduction in gas permeation preventing structures used in applications which require the prevention of gas permeation (for example, pneumatic tires, gas or fluid transporting hoses, etc.) has heretofore been desired. For example, although a rubber composition comprising as a main component a butyl-based rubber such as butyl rubber and halogenated butyl rubbers is used in an inner liner which is provided on the inner surface of a pneumatic tire as a gas permeation preventing layer to retain the inner pressure of the pneumatic tire, rubber compositions comprising a butyl-based rubber as a main component have low gas barrier properties, and therefore when an inner liner is formed using such a rubber composition, it has been necessary to thicken the thickness of the inner liner. Therefore, the use of a rubber composition comprising a butyl-based rubber as a main component has been problematic in weight reduction in tires in order to improve the fuel efficiency of automobiles.
Providing a film of ethylene-vinyl alcohol copolymer (EVOH) which is known to have excellent gas barrier properties, laminated with an elastic surface layer or adhesive layer, on the inner surface of a tire, in order to achieve improvement in the inner pressure-retaining ability and weight reduction of a pneumatic tire, is proposed in, for example, Patent Documents 1 and 2. However, when an EVOH layer is used as a layer which constitutes an inner liner for pneumatic tire, since EVOH has a significantly higher elastic modulus compared to rubbers usually used in pneumatic tires, repeated flexure and tensile deformations subjected to the EVOH layer during the running of the tire result in a reduction in gas barrier properties of the EVOH layer, and as a result, lead to a reduction in the inner pressure-retaining ability of the tire. As a means for solving this problem, Patent Document 3 discloses a technique relating to the use of a resin composition comprising 60 to 99 wt % of an ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 70 mol % and a saponification degree of 85% or more and 1 to 40 wt % of a hydrophobic plasticizer in an inner liner of a pneumatic tire. In addition, Patent Document 4 discloses a technique relating to the use of a modified ethylene-vinyl alcohol copolymer obtained by reacting 100 parts by weight of an ethylene-vinyl alcohol copolymer having an ethylene content of 25 to 50 mol % with an epoxy compound in an amount of 1 to 50 parts by weight with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer in an inner liner of a pneumatic tire. Moreover, Patent Document 5 discloses a technique relating to the use of a tire inner liner comprising a phase of a resin composition comprising a matrix of an ethylene-vinyl alcohol copolymer modified with the epoxy compound and a soft resin which has a Young's modulus lower than that of the modified ethylene-vinyl alcohol copolymer at 23° C. and is dispersed in the modified ethylene-vinyl alcohol copolymer.
However, the inner liners for pneumatic tire obtained by the techniques as described above are not sufficient in inner pressure-retaining ability after fatigue (after tire running), and therefore there is still a need to further improve the fatigue resistance in order to reduce the decrease in gas barrier properties due to fatigue. Also in applications such as gas or liquid transportation hoses, there is a need to achieve weight reduction and to reduce the decrease in gas barrier properties due to fatigue.